TALITHA (Iota Ursae Majoris). Three close (but physically
unrelated) pairs of stars make the feet of Ursa Major, the Great Bear. In Arabic culture, the
three represent the "leaps" of a gazelle, Talitha (Bayer's "Iota"
star) and
Kappa Ursae Majoris making (and meaning) the westernmost
"third leap" (the name actually coming from the number 3). The
other two "leaps," Tania and Alula, are divided into northern and
southern (Tania Australis and
Borealis
and Alula Australis and
Borealis),
but for some odd reason not Talitha, which belongs
exclusively to the northern of the pair.
Talitha, in simplest form
a cooler class A (A7) star 48 light years away, is on closer look
a complex multiple. The main component third- magnitude (3,14) A7
star has a temperature of 8165 Kelvin and a luminosity 9 times that
of the Sun. Though classed from its
spectrum as a "subgiant," a star whose internal hydrogen core is
running (or has run) out of fuel, placement by temperature and
luminosity show it to be a rather youthful 1.7 solar mass star that
has a lot of hydrogen-fusion time left to it. Four seconds of arc
away, in an orbit averaging 132 Astronomical Units in radius, is a
reddish 10th magnitude companion that takes 818 years to make a
full circuit. The companion is itself a double, a pair of class M
(M1) dwarfs that take 40 years to circle each other at a distance
of 10 Astronomical Units (about Saturn's distance from the Sun).
Returning to the bright class A star, it again is double, the
companion, about which nothing is known, taking 11 years to orbit
at a rough distance of 5 or 6 Astronomical Units. From the M star
double, were there an orbiting planet (which almost certainly there
is not), the bright A star would shine nearly 500 times more
brightly than our full Moon, the small companion at most 2.5
degrees away, while from the bright star (again a planet highly
doubtful), the class M double would in combination cast a reddish
light about equal to that of our full Moon, the two at most a bit
over four degrees apart.